I recently got 2 tunes from MPT performance for my 2018 f150 3.5 ecoboost. I got the 87 daily/tow tune and the 91prx. I have only run the 87 tune so far and have noticed a drop in mpg by about 2mpg. Before getting the tune I was reading that most people saw an increase with the tune installed. Has anyone else noticed this issue? I have not been driving hard either to try to gain mpg. Would changing spark plugs help out with this?

 

Did you have tire size changed with the tune? I definitely wouldn't expect an increase. My mpt tune is one of the best for mileage.

 

Yes before the tune I had switched to 285/60r20 and corrected the tire size when I got the tune to calibrate the speedo. What tune are you running?

 

91prx. It gets no better mileage than factory but gets better mileage than some other tunes I have. Your tire size calibration is where the "worse" mileage is coming from.

 

my smiles per gallon increased significantly after getting a tune.